Journal of Physical Chemistry & Biophysics
Open Access

A new method of step height measurement using two laser wavelengths

International Conference and Trade fair on Laser Technology

July 20-22, 2015 Orlando, Florida, USA

Naoyuki Koyama

Scientific Tracks Abstracts: J Phys Chem Biophys

Abstract :

When two laser beams of different wavelength are simultaneously applied to a Michelson interferometer, complicated variation in interference intensity occurs due to the difference in optical path length between the reference beam and the measuring beam. The frequency and wavelength of laser a are νa and λa respectively, and similarly the frequency and wavelength of laser b are νb and λb. Because νa and νb are irrational numbers, not integers, in a strict sense the same intensity variation of the interference does not reappear. In a practical sense, however, the ratio νa:νb can reduce to a simple ratio of whole numbers m:n, and intensity variation from optical path length differences occur periodically. The corresponding period of the optical path length difference is mλa (=nλb). Step height can be measured within half of mλa (=nλb) with measuring error on the order of nanometers. A measuring instrument based on this idea is proposed, and also propose that how optical axes of two-wavelength semiconductor laser coincide with each other by prism.

Biography :

Naoyuki Koyama completed his PhD at the age of 30 years from Tokyo University. He joined Nissan Motor Co., Ltd. Aerospace Division, engaged in developing instruments for quality assurance and had been working in the company till 2010.